"With hindsight the consequences of a large earthquake and tsunami seem obvious, so why didn't the engineers plan for them properly? This is the usual story with systemic risk: In hindsight the problems are obvious, but somehow no one thinks them through beforehand.As already explained, from a complex systems engineering perspective, the key principle is stability. Nuclear power generation is intrinsically unstable. If you walk away from a wind generator or a solar cell when a crisis occurs, not much happens. If you walk away from a nuclear reactor under the wrong circumstances, it can melt down. To cope with the systemic risk one needs to think through all possible scenarios. The experts might be able to plan for all the known failure modes, but it is much harder to anticipate the unknown ones.The prognosis for nuclear accidents based on simple historical extrapolation is disturbing. After roughly 14,000 cumulative years of nuclear plant operation, we have now had three major accidents. If we ramp up nuclear power by a factor of ten, which is necessary to make a significant contribution to mitigate global warming, we will increase from the 442 reactors that we currently have to about 5000. Historical extrapolation predicts that we should then expect an accident of the magnitude of the current Japan disaster about once a year.

But I don't trust the historical method of estimating. Three events are unlikely to properly characterize the tails of the distribution. My personal choice for a really nasty nuclear scenario goes as follows: Assume the developed world decides to ramp up nuclear power. The developing world will then demand energy independence and follow suit. For independence you need both reactors and fuel concentrators. There will be a lot of debate, but in the end the countries with stable governments will get them. With a fuel concentrator the waste products of the reactor can be used to make weapons grade fuel, and from there making a bomb is fairly easy. Thus, if we go down the path of nuclear expansion, we should probably assume that every country in the world will eventually have the bomb. The Chernobyl disaster killed the order of ten thousand people: A nuclear explosion could easily kill a million. So all it will take is for a "stable government" to be taken over by the wrong dictator, and we could have a nuclear disaster.I'm not an actuary, so you shouldn't trust my estimates. To bring the actuaries into the picture, anyone who seriously advocates nuclear power should lobby to repeal the Price-Anderson Act, which requires U.S. taxpayers to shoulder the costs of a really serious accident. The fact that the industry demanded such an act suggests that they do not have confidence in their own product. If the act were repealed, we would have an idea what nuclear power really costs. As it stands, all we know is that the quoted costs are much too low."